Now her sons, the Duke of Cambridge and Prince Harry, have signalled their desire to continue her legacy, noting in a letter to the Terrence Higgins Trust that they had “never known a world without HIV.”

They warned that despite decades of work by campaigners and huge strides in the development of treatments, a stigma still blighted sufferers of the disease.

They said their mother had “believed passionately” in the work of the Trust and called on their generation to "pick up the sword and continue the fight".

In the letter, sent to congratulate the HIV charity on its 30th anniversary, the brothers wrote: “We have grown up knowing of the devastating impact this virus has on lives, on families, on communities.

"We know, too, that HIV can be treated and the lives of sufferers extended by many years. However, there is still a stigma which blights sufferers of the disease, even today.”

Related Articles

They said the Trust, which was founded in 1982 by friends of Terrence Higgins, 37, one of the first people in the UK to die of Aids, had been “the other constant in this story of our generation.”

Genevieve Edwards, director of communications for the Trust, said they were “thrilled” that the princes had pledged such public support for their work, particularly as the ongoing stigma made it difficult to raise funds.

“Diana was instrumental in those early days in challenging people’s fears about HIV,” she said. “She also did a lot privately, regularly visiting the Lighthouse hospice in Kensington, completely unannounced and without an entourage, just to talk to staff and volunteers. Charles did his bit too, publicly giving blood at a time when there were such real fears that people had stopped donating.

“William is the same age as our charity. Aids has been a constant in their lives but we can now see an end to new infections, with quite simple steps it is in our grasp. We do not need to put up with subsequent generations never knowing a world without HIV.”

She said that around 25,000 people, a quarter of HIV sufferers in the UK, did not know that had the disease but could be treated if they took a simple £10 test, adding up to 40 years to their life expectancy.

Diana, Princess of Wales, was the first member of the Royal Family to have contact with Aids victims, sitting with an HIV sufferer and holding his hand in the late 1980s.

In their letter to the charity, her sons said: "Our generation has never known a world without HIV.”

They praised the “inspirational” work of the Trust’s staff and volunteers whose work had transformed the lives of sufferers.

“They have prevented countless new infections, supported thousands of people to live healthy lives with HIV, and campaigned tirelessly to gain a greater public understanding of the personal, social and media impact of HIV,” they wrote.

“The wonderful legacy he inspired lives on today in his trust.”

They added: “The fight against HIV started 30 years ago. Our generation must pick up the sword and continue the fight. There is still no cure or vaccine. However, we know it is possible to prevent HIV from spreading further in the future.

"Terrence Higgins Trust will be to the fore in this, and for that reason, and because our mother believed so passionately in the work of the trust, we wholeheartedly congratulate you on 30 years of selfless service to others."

A photograph of the princes with their mother will go under the hammer at the charity's 30th anniversary auction in March.